Weldable, corrosion-resistant AIMG alloys, especially for manufacturing means of transportation

ABSTRACT

A weldable, corrosion resistant aluminum-magnesium alloy consisting essentially of 3 to 5% by weight magnesium (Mg), 0.05 to 0.15% by weight zirconium (Zr), 0.05 to 0.12% by weight manganese (Mn), 0.01 to 0.2% by weight titanium (Ti), 0.05 to 0.5% by weight of one or more elements selected from the scandium group of the Periodic Table and/or terbium (Tb), wherein at least 0.15% by weight scandium (Sc) is included with or without terbium (Tb) and with or without 0.05 to 0.35% by weight of one or more elements from the lanthanide series, the balance being aluminum (Al), and unavoidable contaminants not exceeding 0.2% by weight silicon (Si).

BACKGROUND OF THE INVENTION

The invention relates to a weldable, corrosion-resistant, high-magnesiumcontent aluminum-magnesium alloy, which contains a ternaryaluminum-scandium-zirconium phase as an essential component. Such analloy is disclosed in U.S. Pat. No. 5,624,632, for application inaerospace construction due to its low density, high strength andcorrosion resistance. Adding rare earth or rare earth-like elementsgenerates dispersoids in the aluminum-magnesium alloy, which produce ahigher strength and corrosion resistance. The aforesaid U.S. patent issilent as regards the weldability of such an alloy.

SUMMARY OF THE INVENTION

An object of this invention is to provide a weldable,corrosion-resistant, high magnesium content aluminum-magnesium alloy,which is at least as good as the known alloy with respect to strengthand corrosion resistance and exhibits a high recrystalization thresholdand good weldability. This and further objects of the invention areachieved by a weldable, high magnesium-content aluminum-magnesium alloyconsisting essentially of 3 to 5% by weight magnesium, 0.05 to 0.15% byweight zirconium, 0.05 to 0.12% by weight manganese, 0.01 to 0.2% byweight titanium, 0.05 to 0.5% by weight of at least one element selectedfrom the scandium group of the Periodic Table, wherein scandium ispresent as a mandatory element optionally with terbium and/or 0.05% to0.35% by weight of one or more elements in the lanthanide series, thebalance being aluminum and unavoidable contaminants not exceeding 0.2%by weight silicon.

DETAILED DESCRIPTION

In comparison with the above described known alloy, in U.S. Pat. No.5,624,632 the new alloy of the invention exhibits primarily a distinctlylower manganese content, whereby an improved corrosion resistance wassurprisingly obtained, especially in a heat-treated state of parts madefrom this alloy, e.g., when cold-formed parts are subjected to anelevated temperature over a prolonged period of time. It was found thatthese positive properties are determined by the ratio of manganese toscandium. An improved corrosion resistance is found when the ratio of Mnto Sc is less than 2. Along with acting as a grain growth inhibitor, thetitanium content (not present in the described known alloy) helps toincrease strength, since titanium can replace the zirconium in theternary Al—Sc—Zr phase, wherein the solubility of titanium is lower thanthat of zirconium, however.

It has also been found that scandium can be replaced by terbium, atleast within certain limits. However, more terbium than the amount ofscandium being replaced must be added to achieve constant properties.

A particularly favorable alloy for motor vehicles ships and aircraftstructures contains at least 0.15% by weight scandium. One of moreelements from the Lanthanide series is preferably included in amountsranging from 0.05 to 0.35% by weight. The alloy tolerates siliconcontamination of up to 0.2% by weight, the dynamic properties of thealloy deteriorating above this level.

Although the invention is disclosed with reference to particularcompositions, it will become apparent to those skilled in the art thatnumerous modifications and variations can be made which will fall withinthe scope and spirit of the invention as defined by the attached claims.

What is claimed is:
 1. A weldable, aluminum-magnesium alloy comprising aternary aluminum-scandium-zirconium phase and consisting essentially of3 to 5% weight magnesium, 0.05 to 0.15% by weight zirconium, 0.05 to0.12% by weight manganese, 0.01 to 0.2% by weight titanium, 0.05 to 0.5%by weight of at least one element from the group consisting of scandiumand the lanthanide series, wherein at least scandium is present, thebalance being aluminum, and unavoidable contaminants not exceeding 0.2%by weight silicon.
 2. An aluminum-magnesium alloy as claimed in claim 1,wherein the ratio of manganese to scandium is less than
 2. 3. Analuminum-magnesium alloy as claimed in claim 1, wherein at least 0.15%by weight of scandium is present in the alloy.
 4. An aluminum-magnesiumalloy as claimed in claim 1, wherein said at least one element from saidgroup in addition to scandium comprises terbium.
 5. Analuminum-magnesium alloy as claimed in claim 1, wherein said at leastone element from the said group in addition to scandium is 0.05 to 0.35%by weight of an element in the lanthanide series.
 6. Analuminum-magnesium alloy as claimed in claim 5, wherein said at leastone element in the lanthanide series is neodyme, europium, gadolinium,dysprosium, holmium or erbium.
 7. Rolled, extruded, welded or forgedcomponent of an aircraft, a ship or a motor vehicle consisting of anAlMg alloy according to claim 1.